L-type heat sealing device with uniform sealing pressure

ABSTRACT

A heat sealing device includes a frame rotatably supporting gears and comprising four fixed upright guide rods. Upper and lower members, in the form of U-shape, are movable along the guide rods between engaging position and separated position. The upper and lower members each have four racks respectively engaging the gears whereby the upper and lower members are movable synchronously. A power cylinder has a rod mounted to the upper member for driving the upper and lower members toward/away from each other. Heating elements are mounted to the upper and lower members and are substantially opposite to each other. The upper and lower members are maintained substantially parallel to each other during the movement thereof whereby a uniform sealing pressure is applied to the heating elements of the upper and lower members to achieve high quality sealing results.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to an L-type heat sealing device, and in particular to a heat sealing device operative with uniform sealing pressure for excellent and efficient sealing operation.

[0003] 2. The Related Art

[0004] Plastic films have been widely used to wrap and pack consumer products, such as foods, books, video/audio compact disks for protecting the products from contamination and damage. A packaging machine is required to warp the package film around the product. The package film that is wrapped around the product is then heated along sealing line by a sealing device to seal the package film around the product so as to completely enclose the product with the package film.

[0005]FIG. 7 shows a conventional L-type heat sealing device for the package film which is generally designated with reference numeral A. The conventional heat sealing device A comprises an upper member A1 and a lower member A2 connected to each other by a pivot A3 whereby the upper member A1 is rotatable with respect to the lower member A2, which is generally fixed, about the pivot A3 to engage with/disengage from each other. Both the upper and lower members A1, A2 are provided with heating elements B so that when the upper and lower members A1, A2 engage each other with package films sandwiched therebetween, the heating elements B are brought into contact with the package films for heating and thus sealing the package films together.

[0006] However, since the upper and lower members A1, A2 are pivoted to each other at for example a rear end, the pressure applied by the upper and lower members A1, A2 to the package films is not uniformly distributed along the upper and lower members A1, A2. In addition, the exact time that a portion of the upper member A1 engages a corresponding portion of the lower member A2 varies along the upper and lower members A1, A2. This results in potentially poor quality of sealing.

[0007] Due to the non-uniform distribution of pressure between the upper and lower members A1, A2 and due to the variable time when portions of the upper and lower members A1, A2 contact each other, the heating elements B cannot be actuated before the upper and lower members A1, A2 completely engage each other, otherwise the time period during which the heating elements B are in operation must be extended so as to ensure acceptable sealing quality. This causes problems, such as precise calculation of the time when the heating elements B are to be actuated and requirement of sophisticated control mechanism. In addition, the extended heating period reduces the operation efficiency of the sealing device.

[0008] A technically feasible solution for the above problems is to drive the upper and lower members A1, A2 independently. This solution, however, requires independent drivers for the upper and lower members A1, A2. The overall structure is complicated and the control is sophisticated. Costs are thus increased. Further, noises caused by the operation of the independent drivers are greater than a single driver system.

[0009] Thus, it is desired to have a heat sealing device for alleviating the above disadvantages.

SUMMARY OF THE INVENTION

[0010] An object of the present invention is to provide a heat sealing device comprising upper and lower members engageable with each other in such a way to provide a uniform pressure distribution along the members.

[0011] Another object of the present invention is to provide a heat sealing device which provides a uniform sealing pressure with a simple structure.

[0012] A further object of the present invention is to provide a heat sealing device that provides excellent sealing quality without extended period of heating.

[0013] Yet a further object of the present invention is to provide a heat sealing device comprising movable upper and lower members that are driven by a single driving device so as to simplify the structure thereof.

[0014] To achieve the above objects, in accordance with the present invention, there is provided a heat sealing device comprising a frame rotatably supporting gears and comprising four fixed upright guide rods. Upper and lower members, in the form of U-shape, are movable along the guide rods between engaging position and separated position. The upper and lower members each have four racks respectively engaging the gears whereby the upper and lower members are movable synchronously. A power cylinder has a rod mounted to the upper member for driving the upper and lower members toward/away from each other. Heating elements are mounted to the upper and lower members and are substantially opposite to each other. The upper and lower members are maintained substantially parallel to each other during the movement thereof whereby a uniform sealing pressure is applied to the heating elements of the upper and lower members to achieve high quality sealing results.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which:

[0016]FIG. 1 is a perspective view of a heating sealing device constructed in accordance with the present invention;

[0017]FIG. 2 is a perspective view similar to FIG. 1 with portions of the heat sealing device being removed (shown with phantom lines) to show inside details thereof;

[0018]FIG. 3 is a perspective view showing a transmission system of the heat sealing device of the present invention;

[0019]FIG. 4 is a front view showing upper and lower members of the heat sealing device of the present invention in an initial, separated position;

[0020]FIG. 5 is a front view similar to FIG. 4 but showing the upper and lower members of the heat sealing device moving toward each other;

[0021]FIG. 6 is a perspective view showing a package machine in which the heat sealing device of the present invention is incorporated; and

[0022]FIG. 7 is a perspective view showing a conventional heat sealing device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] With reference to the drawings and in particular to FIGS. 1-4, a heat sealing device, generally designated with reference numeral 100, comprises a frame 10 which can be of any construction. In embodiment illustrated, the frame 10 comprises four support plates 11 arranged on four corners of a rectangle. A gear 12 is rotatably mounted to an inner surface of each support plate 11. The frame 10 comprises a bottom board 14 fixed to the support plates 11 or alternatively and as shown in FIG. 6 the bottom board 14 is fixed to a chassis 210 of a package machine 200 that incorporates the heat sealing device 100. Four guide rods 13 respectively adjacent each support plate 14 extend upward from the bottom board 14.

[0024] The heat sealing device 100 comprises an upper movable member 20 and a lower movable member 30. Each of the upper and lower members 20, 30 comprises four bearing elements 21, 31 for slidably engaging the guide rods 13 whereby the upper and lower members 20, 30 are guided to move along the guide rods 13. In the embodiment illustrated, the upper and lower members 20, 30 are made U-shaped having two lateral segments connected by an end segment (both not labeled). The upper and lower members 20, 30 are substantially opposite to and parallel to each other. The parallel relationship is consistently maintained during the movement of the upper and lower members 20, 30. This will be further discussed hereinafter.

[0025] Heating means 21′, 31′ respectively comprised of two sections are respectively mounted to one of the lateral segments and the end segment of the upper and lower members 20, 30. The heating devices 21′, 31′ are arranged to be substantially opposite to each other whereby when the upper and lower members 20, 30 move toward each other, the heating devices 21′, 31′ are brought into engagement with each other for heating and sealing a package film C that packages an article D to be packaged (FIG. 6).

[0026] The heat sealing device 100 comprises a transmission system for synchronously moving the upper and lower members 20, 30 with respect to each other with the upper and lower members 20, 30 maintained substantially parallel to each other. In the embodiment illustrated, the transmission system comprises racks 22, 32 respectively mounted to the upper and lower members 20, 30 and engageable with each gear 12 whereby the upper and lower members 20, 30 are movable synchronously with respect to each other in opposite directions, either moving toward each other or moving away from each other.

[0027] A driving device 40 is mounted to the frame 10 and mechanically coupled to the transmission system for selectively moving the upper and lower members 20, 30 toward each other and away from each other. The driving device 40 can be any known power devices, such as a power cylinder shown in the drawings. Other power devices, such as electric motors, can also be employed to move the upper and lower members 20, 30.

[0028] The power cylinder 40 is arranged above the frame 10 and comprises a rod 41 extending downward. The rod 41 is extendable and retractable with respect to the cylinder 40. An end member 42 is mounted to the rod 41 whereby the end member 42 is movable with the rod 41 between an upper position and a lower position. The end member 42 straddles between and is connected to the lateral segments of the upper member 20 whereby the upper member 20 is movable with the end member 42. The lower member 30 is movable synchronously with the upper member 20 due to the rack-gear engagement between the racks 22, 32 of the upper and lower members 20, 30 and the gears 13. Thus, when the end member 42 is moved to the lower position, the upper and lower members 20, 30 (or the heating means 21′, 31′ thereof) engage each other. When the end member 42 is moved to the upper position, the upper and lower members 20, 30 are separated from each other to allow the article D and the package film C to pass therebetween.

[0029]FIG. 4 shows the relationship between the upper and lower members 20, 30 when the rod 41 of the power cylinder 40 is at the upper position where the upper and lower members 20, 30 are separated from each other. FIG. 5 shows the relationship between the upper and lower members 20, 30 when the upper and lower members 20, 30 are being moved toward each other.

[0030]FIG. 6 shows a package machine 200 in which the heat sealing device 100 of the present invention is incorporated. The package machine 200 comprises a chassis 210 to which the frame 10 of the heat sealing device 100 of the present invention is fixed. A conveyor system 220 is arranged inside the chassis 210 for conveying the article D to be packaged through the heat sealing device 100. The package machine 200 can further comprise a conveyor system 230 for forwarding the article D into the heat sealing device 100. The package film C is guided into the heat sealing device 100 with the article D to enclose the article D.

[0031] To this point, it is clear that the present invention provides a heat sealing device that possesses the following advantages:

[0032] (1) The upper and lower members 20, 30 are maintained parallel to each other when the heating means 21′, 31′ is brought into engagement with each other whereby a uniform sealing pressure can be applied to the package film C to obtain excellent sealing quality.

[0033] (2) The heating means 21′, 31′ does not need to be energized for an extended period to obtain desired sealing result. The operation efficiency of the package machine can thus be enhanced.

[0034] (3) The heat sealing device 100 has a simple and reliable structure. No sophisticated control elements are needed.

[0035] (4) The heat sealing device 100 employs a single power device to drive both the upper and lower members 20, 30 synchronously whereby costs are reduced. Noise vibration of the package machine are reduced.

[0036] Although the present invention has been described with reference to the preferred embodiment thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims. 

What is claimed is:
 1. A heat sealing device comprising: a frame; upper and lower members movably supported by the frame, the upper and lower members each comprising a heating device substantially opposite to and engageable with each other for performing a heat sealing operation on a package film; a transmission system comprising a gear rotatably mounted to the frame and racks mounted to the upper and lower members and engaging the gear whereby the upper and lower members are movable in synchronization with each other; and a driving device coupled to one of the upper and lower members to move the upper and lower members with respect to each and thus bringing the heating devices of the upper and lower members to engage each other.
 2. The heat sealing device as claimed in claim 1 further comprising guide rods fixed to the frame for guiding the movement of the upper and lower members.
 3. The heat sealing device as claimed in claim 2, wherein the upper and lower members comprise bearing means slidable along the guide rods for guiding the movement of the upper and lower members.
 4. The heat sealing device as claimed in claim 2, wherein the frame comprises a bottom board from which the guide rods extend.
 5. The heat sealing device as claimed in claim 1, wherein the frame comprises a support plate to which the gear is rotatably mounted.
 6. The heat sealing device as claimed in claim 1, wherein the upper and lower members each comprise a U-shaped frame having lateral segments connected by an end segment, the U-shaped frames being substantially opposite to each other and maintained parallel to each other, the sealing device comprising sections mounted to one of the lateral segments and the end segment of U-shaped frame of the upper and lower members.
 7. The heat sealing device as claimed in claim 1, wherein the driving device comprises a power element coupled to the upper member for moving the upper and lower members.
 8. The heat sealing device as claimed in claim 7, wherein the power element comprises a power cylinder having a rod connected to the upper member.
 9. The heat sealing device as claimed in claim 6, wherein the driving device comprises a power cylinder having a rod, an end member being attached to the rod, the end member straddling between and fixed to the lateral segments of the upper member. 